Film deposition is a well-known processing technique for depositing thin films on different types of substrates. One technique for depositing thin films is sputtering, which can be advantageously used in the manufacture of magnetic storage media. In film deposition, the maintenance of a controlled environment in which the process occurs is crucial to ensuring the integrity of the deposited film.
Co-pending patent application Ser. No. 08/121,959, published as Publication No. PCT/US92/00722, discloses an in-line sputtering apparatus which is utilized to manufacture magnetic recording media for use in Winchester-type hard disk drives. An integral component of the in-line sputtering apparatus disclosed in publication PCT/US92/00722 is the fact that it utilizes an overhead transport drive system to move substrates through the process environment. The transport system disclosed in publication PCT/US92/00722 is designed to move the substrates through the system in an efficient and flexible manner, while reducing contamination which can result from the interaction of mechanical components in the drive as the substrates are transported through the system.
The evacuated environment of a sputtering chamber such as that utilized in Publication No. PCT/US92/00722 includes an inert gas, typically argon, with one or more substrates remaining static or, as in Publication No. PCT/US92/00722, being transported through the sputtering chamber during deposition. In manufacturing magnetic recording media, the cleanliness of the chamber is critical to ensuring the integrity of the manufactured component. The media must be free from contamination in order to operate effectively, and to optimize the film integrity to allow for higher data capacities in the film and higher storage capacities in the resultant disk drive.
The transport system in Publication No. PCT/US92/00722 is generally referred to as an "overhead" transport apparatus. An overhead apparatus is one that secures and supports at least a majority of the weight of the substrate at the top of the substrate, such that the substrate hangs from the transport mechanism as the substrate is transported through the apparatus. In Publication No. PCT/US92/00722, the transport system supports all of the weight of the pallets at the top of the pallet, so that the pallet hangs from the transport system with its lower portion free. Certain types of transport systems in in-line sputtering apparatus have utilized systems which carry the substrate and support both the top and the bottom portion of the pallet. Generally, overhead drive systems are disfavored in sputtering environments since such systems can generate more particulate contamination than bottom drive systems due to the fact that the drive's mechanical components are above the surface of the substrate, and mechanical interaction between the mechanical components of the drive system can cause contamination to fall on the substrate as the substrate is moved through the system. However, utilizing a top drive system allows the use of larger substrates and substrate-carrying pallets since top drive systems can support weight with greater stability than a bottom drive system.